The present invention is directed to apparatus having capability of a digital readout of time by a visual observation of indicia imprinted on or carried by a plurality of rotatable members which may be indexed to a viewing window.
Various forms and arrangements of drive mechanisms have been employed in apparatus of this type for purposes of a timed incremental advance of the rotatable members including units-of-minutes, tens-of-minutes, and hour members. Further, various structural configurations have been employed in the past to maintain these rotatable members in the position to which and from which they are moved by the drive mechanism.
The present invention is an improvement in apparatus of this type and further provides structure for maintaining an amount of clearance between the rotatable members. As may be apparent, ambient conditions of heat and cold will have a decided effect on the amount of clearance between the rotatable members, some amount of which without being insufficient or excessive should be maintained for proper operation of the readout device. Thus, an insufficient clearance would result in a binding of the rotatable members necessitating greater torque for movement, and on the other hand, excessive clearance possibly would result in a failure of the driving engagement of the drive mechanism to militate against a positive advancing operation.
The structure for maintaining a clearance between the rotatable members is denominated an endshake element which is received between the rotatable member of highest order and the housing in which the members are disposed. Particularly, the rotatable members are supported on a shaft and the rotatable member of lowest order is secured to the shaft. The endshake element, likewise received on the shaft, includes camming means on one side of a plate-like body, which camming means cooperate with like camming means on the housing in the region surrounding an aperture which receives and provides support for one end of the shaft. Both camming means are defined by a plurality of inclined surfaces and through rotation of the endshake element relative to the housing the inclined surfaces of the camming means ride one on the other thereby to relocate the endshake element axially in the housing. Varying degrees of clearance between the rotatable members may be derived, accordingly. And, the positioning of the endshake element may be maintained after adjustment by detent means. This structure will be described with greater particularity below. Likewise, the structure for a timed and a setting advance of the rotatable members will also be described. Briefly, however, the advancing mechanism comprises a plurality of pinions supported for rotation adjacent the rotatable members, there being an input drive to each respective pinion while that pinion drives the rotatable member of next higher order. The pinions are freely mounted on a supporting shaft and are in engagement directly with the teeth of a continuous gear carried by a rotatable member of higher order, while in engagement intermittently with the teeth of a mutiliated gear carried either by a rotatable member of lower order or the timed advance mechanism constituting the input drive depending upon which pair of rotatable members are being considered. For this purpose, a plurality of the pinion teeth at equidistant spacing therearound are extended axially to span the gap between a pair of rotatable members or the timed advance mechanism, as the case may be. Thus, each pinion is jogged in advance as the mutilated gear moves into engagement with the axial extension of one of the teeth of the pinion which causes a similar advance through engagement with the continuous gear. Except during those times as the pinion is jogged by engagement with the mutilated gear, two adjacent pinion teeth of those which are axially extended ride the surface connecting the mutilated gear thereby to "lock" that pinion against movement. Adjacent pinions are similarly "locked" and there is no movement of the rotatable members except through a driving advance.
Other features and advantages of the present invention will become apparent as the specification continues.